The swing-type operation machine such as a hydraulic excavator includes an under carriage and a swing table mounted on the under carriage so as to swing thereon. On the swing table is mounted an operator station on which are installed a seat and equipment for operation. An engine is installed on the lower side of the operator station at the back of the seat (see, for example, patent documents 1 and 2).
The outer circumferential edge of the swing table of the swing-type operation machine is formed in a size as small as possible to decrease the probability of interference with the surrounding obstacles when undergoing the swinging operation as well as to maintain good circumferential view from the operator's seat. Therefore, the operator station, engine and the like are installed in a limited space together with other equipment and devices.
When the operator station is mounted on the swing table, a pair of right and left legs is provided on the rear part of the seat to avoid the engine (see, for example, patent document 1), or a counter weight installed on the outer side of the engine in parallel therewith is provided with a pair of right and left support poles (see, for example, patent document 2).
Patent document 1: JP-A-2004-143672
Patent document 2: JP-A-2004-285699